The USB I/O Bit allows you to send and receive digital audio and control voltages to and from a computer. When using in conjunction with a Digital Audio Workstation (DAW), you can record your sounds directly into a computer without the need of an external audio interface. You can also send audio from a computer into the littleBits system to manipulate it, for example with the filter and delay Bit.

The w27 USB I/O Bit features 44.1K/12-bit audio conversion for high quality sound. It is also "DC coupled," which means that in addition to sending and receiving signals like music, it can also send and receive control voltages. Sending and receiving control voltages allows you to use software programs like Max, PD, and CV Toolkit with the USB I/O Bit to control other Bits. You can also use Bits to create hardware controls for your software. The USB I/O Bit will appear to your computer as an audio interface and its input and output routing can be selected as with any other audio interface. The Bit can only be selected as either an input or output device at a given time but multiple USB I/O Bits can be used at once.